Process to manufacture shaft and guide pins as used for planetary systems

ABSTRACT

“PROCESS TO MANUFACTURE SHAFT AND GUIDE PINS AS USED FOR PLANETARY SYSTEMS”, the present invention refers to the technical field of automotive parts, more specifically to a process to manufacture a shaft ( 1 ) and guide pins ( 2 ) as used for planetary systems, which purpose is to improve the strength, durability and to reduce the costs of final products.

BACKGROUND

The present invention refers to the technical field of automotive parts,more specifically a process to manufacture a shaft and guide pins asused for planetary systems, which purpose is to improve the strength,durability and to reduce the costs of final products.

The search to reduce the emission level of automotive vehicles has beena constant concern for automakers. One of the alternatives being dailyused and improved is to reduce the weight of vehicles, to provide areduction in fuel consumption and consequent reduction in the level ofemissions.

Based on this trend, manufacturers of implements for the electricalsystem of vehicles have concentrated efforts to reduce the weight/powerratio of components as used in the system.

One of the solutions found was the use of planetary gears reductionsystems for starter motors, which provide reduction in measurements andweight of motors, not changing their performance.

The planetary gears system as used for starter motors is constituted bya set of reduction gears, fixed to the shaft by guide pins, to which thesun gear and the crown are attached. The main function of the system isto provide higher available torque at the exit shaft.

STATE OF THE ART

Most manufacturers use heat treatment by electromagnetic induction inthe shaft manufacturing process, with consequent high cost and lowproductivity in comparison with the present invention.

DISCLOSURE OF THE INVENTION

The present invention uses heat treatment by carburizing, quenching andtempering, thus providing constant hardness throughout the part,presenting the great advantage of a significant reduction in wearingcaused at the edge of the shaft, by the friction with reduction gears.

The process as proposed has the object to: improve the resistance anddurability of the shaft (1) and guide pins (2) of the planetary systemas used in starter motors; provide an increase in productivity, due tothe quick process; and reduce the final cost of parts.

Disclosure of the Process

In the present process, guide pins of reduction gearings are previouslytreated by the carburizing, quenching and tempering. After thetreatment, they are grinded and then assembled to the edge of the shaft.

Subsequently, the shaft receives heat treatment by carburizing,quenching and tempering, which provides for constant hardness throughoutthe part, thus increasing wearing resistance in friction regions betweenturning parts.

Carburizing is a heat-chemical diffusion treatment which object is toincrease the rate of carbon on the part surface. It may be effected insolid, paste, liquid, gaseous or plasma means.

In the process at issue, carburizing is used by gaseous means, thusoffering the following advantages:

to improve the content of carbon and consequently the hardened layer;

stability of the carburizing mixture during the whole carburizingprocess;

to avoid oxidization;

to allow direct annealing after hardening; and

quick carbon penetration.

Quenching is a heat treatment consisting in submitting steel to a heatcycle successively comprising:

heating intended to reach a temperature-stable stage (austenite) bymeans of transformation and eventual solubilization of otherconstituents;

appropriate cooling rate as per the corresponding “S” curve, practicedsince that temperature, so-called tempering, up to the treatment of thecooling means.

Tempering is a heat treatment effected over a tempered product, with theobject to change it so to grant characteristics of use as desired. Thistreatment forms a structure which is closer to the state ofphysical-chemical balance than the one obtained by quenching. Theseoperations as a whole are called “quenching and tempering”. We advisethe tempering to be made immediately after quenching.

Objects, advantages and further important characteristics of theinvention at issue may be more easily understood when read jointly withthe attached figure, wherein:

FIG. 1 shows an exploded view of the planetary system as used in startermotors.

As we can see from the attached figure showing and integrating thepresent description of the invention for “Process to Manufacture Shaftand Guide Pins as Used for Planetary Systems”, it is comprised by theuse of heat treatments of carburizing, quenching and tempering, in ashaft (1) and guide pins (2) of the planetary systems as used forstarter motors.

FIG. 1 shows an exploded view of the planetary system as used forstarter motors, showing the crown (A), the shaft (1), the shaft edge(B), guide pins (2), reducing gears (C), cover (D), sun gear (E) and thearmature (F).

1. “PROCESS TO MANUFACTURE SHAFT AND GUIDE PINS AS USED FOR PLANETARYSYSTEMS”, comprised by the use of heat treatments of carburizing,quenching and tempering, in a shaft (1) and guide pins (1) of theplanetary systems as used for starter motors.
 2. “PROCESS TO MANUFACTURESHAFT AND GUIDE PINS AS USED FOR PLANETARY SYSTEMS” of claim 1,characterized by the previous heat treatment of the guide pins (2) bymeans of a carburizing, quenching and tempering process.
 3. “PROCESS TOMANUFACTURE SHAFT AND GUIDE PINS AS USED FOR PLANETARY SYSTEMS” of claim1, characterized by the heat treatment by means of carburizing,quenching and tempering of the whole shaft (2), after guide pins (2) areassembled.